Negative feedback is a universal control mechanism that lets a system's output throttle its input. If an engine revs up,negative feedback tapers its power source. But if the engine slows down, it re-opens the power source, or keeping output reliably regular. This is an example of a negative feedback that can be found in many systems. In biology,for example, genes under negative regulatory feedback increase (or decrease) their expression in response to falling (or rising) concentrations of the gene product.
Source: phys.org